The present invention relates to a latch needle adapted for use in textile machines, such as knitting machines or knitting looms.
For the manufacture of knit ware latch needles of the prior art have been known which have an elongated shank carrying a hook at an end and which are further provided with a latch pivotally supported in a longitudinal sawslot. In one position the latch is, with its end, in contact with the hook (closed position). The latch may be pivoted away from the hook into its reverse position for opening the hook.
A needle of the above type is disclosed, for example, in German Offenlegungsschrift (Application Published Without Examination) DE OS 27 14 607. For dampening the impact energy of the latch in the rearward position, a first longitudinal slot, open in the direction of the needle back, is adjoined by a second longitudinal slot. The latter is disposed below the reverse latch position and has a depth which is greater than one half of the height of the needle shank. The structuring of a latch needle according to DE OS 27 14 607 (also referred to in the art as a dual-slot needle) increases the elasticity of the shank cheeks and thus has a dampening effect.
Further, German Offenlegungsschrift (Application Published Without Examination) DE OS 43 24 232 describes a latch needle which, below the seating surface for the latch in its reverse position, is provided with means constituting an aperture extending from the needle breast to the needle back. This measure increases the deformability of the shank cheeks, thus generating a dampening effect.
It is a common characteristic of the needles described in the above patent documents that in addition to the sawslot in which the latch is pivotally held, they have additional recesses, for example a slot or an aperture, requiring additional process steps in their manufacture.
Further, German Patent No. DE 43 34 051 C1 discloses a needle which, for receiving the latch, has a sawslot starting from the needle breast. The sawslot, relative to the length direction of the shank, has essentially parallel-bordering flanks. At the hook-side end and the opposite end of the sawslot obliquely arranged, arcuate end faces are provided, so that, viewed from the needle breast, the length of the sawslot, relative to the length direction of the shank, decreases inward, that is, toward the depth of the sawslot.
The sawslot is provided at its underside with an aperture open toward the needle back. The aperture is bordered by parallel flanks and has at its hook-side end as well as at its opposite end a small, preferably planar end surface oriented perpendicularly the length direction of the shank.
The aperture leading to the needle back may be utilized for removing from the sawslot dirt which gathers therein during the knitting process.
Further, German Patent No. 586678 describes a latch needle having a sawslot which flares in a funnel-like manner toward the needle back. Relative to the length direction of the shank, the sawslot is bordered by two cheeks, whose inner surfaces form an acute angle with one another. The length of the sawslot increases toward the needle back in the length direction of the shank. Similarly, the length of the sawslot increases toward the needle breast from a short (viewed in the length direction of the shank), approximately mid region of the sawslot.
At the side oriented toward the latch and the needle breast, particularly the hook-side end of the sawslot is formed by a slightly arcuate inclined surface which forms an acute angle with the length direction of the shank. Although the enlargement of the sawslot toward the needle back improves dirt removal according to the earlier noted patent document, it cannot be excluded that the latch, as it closes, presses dirt into the adjoining end surface of the sawslot, whereby a solid dirt body is being formed.
A similar effect may appear in latch needles which are provided with a latch spring for supporting selected pivotal positions of the latch. Such a needle is described, for example, in German Auslegeschrift (Application Published After Examination) DE-AS 1113537. In this needle too, the end surface of the sawslot adjoining the hook and the end surface opposite the hook, are inclined upward, so that as the latch moves, a dirt cushion may be build up on those surfaces. The passage toward the needle back blocked by the latch makes a self-cleaning and dirt removal difficult.
Patent Application P 102004049069.9, not yet published on the filing date of the present application, discloses a latch needle having a spring-supported latch, in which the latch spring is inserted into the sawslot from the needle back. As viewed from the needle back, the length of the sawslot measured in the length direction of the shank is reduced, while its depth increases. At the needle breast the hook-side end surface of the sawslot terminates in a small surface which is oriented perpendicularly or at an obtuse angle to the length direction of the shank and which faces away from the needle breast. This surface is disposed in such a manner that the latch, as it closes, just touches the end of this surface when the latch attains its closed position.
By means of such a measure the buildup of dirt cushions on an end surface of the sawslot by the closing latch may be avoided.